X40431 XICOR [Xicor Inc.], X40431 Datasheet - Page 5

• Manufacturer Part Number: X40431
• Description: 4kbit EEPROM, Triple Voltage Monitor with Integrated CPU Supervisor
• Manufacturer: XICOR [Xicor Inc.]

X40430/X40431 – Preliminary Information
Figure 3. V
WATCHDOG TIMER
The Watchdog Timer circuit monitors the microproces-
sor activity by monitoring the SDA and SCL pins. The
microprocessor must toggle the SDA pin HIGH to LOW
periodically, while SCL also toggles from HIGH to LOW
(this is a start bit) followed by a stop condition prior to
the expiration of the watchdog time out period to pre-
vent a WDO signal going active. The state of two non-
volatile control bits in the Status Register determine
the watchdog timer period. The microprocessor can
change these watchdog bits by writing to the X40430/
31 control register (also refer to page 20).
Figure 4. Watchdog Restart
V1, V2 AND V3 THRESHOLD PROGRAM
PROCEDURE
The X40430 is shipped with standard V1, V2 and V3
threshold (V
values will not change over normal operating and stor-
age conditions. However, in applications where the
standard thresholds are not exactly right, or if higher
REV 1.2.3 11/28/00
SCL
SDA
WDO
SCL
SDA
TRIPX
TRIP1,
.6µs
Set/Reset Conditions
0
A0h
V
V
TRIPX
TRIP2,
1.3µs
V
TRIP3
(X = 1, 2, 3)
Timer Start
7
) voltages. These
0
V
www.xicor.com
CC
/V2MON/V3MON
7
precision is needed in the threshold value, the X40430
trip points may be adjusted. The procedure is described
below, and uses the application of a high voltage control
signal.
Setting a V
There are two procedures used to set the threshold
voltages (V
be stored is higher or lower than the present value. For
example, if the present V
V
into the V
lower than the present setting, then it is necessary to
“reset” the V
Setting a Higher V
To set a V
higher than the present threshold, the user must apply
the desired V
sponding input pin (Vcc(V1MON), V2MON or V3MON).
The Vcc(V1MON), V2MON and V3MON must be tied
together during this sequence. Then, a programming
voltage (Vp) must be applied to the WDO pin before a
START condition is set up on SDA. Next, issue on the
SDA pin the Slave Address A0h, followed by the Byte
Address 01h for V
V
V
initiates the programming sequence. Pin WDO must
then be brought LOW to complete the operation
TRIPx
TRIP3
TRIPx
V
P
0
, and a 00h Data Byte in order to program
. The STOP bit following a valid write operation
is 3.2 V, the new voltage can be stored directly
00h
TRIPx
TRIPx
TRIPx
TRIPx
TRIPx
TRIPx
cell. If however, the new setting is to be
), depending if the threshold voltage to
threshold to a new voltage which is
Voltage (x=1, 2, 3)
voltage before setting the new value.
Characteristics subject to change without notice.
TRIP1
TRIPx
7
threshold voltage to the corre-
, 09h for V
Voltage (x=1, 2, 3)
TRIPx
t
WC
is 2.9 V and the new
TRIP2
, and 0Dh for
5 of 24